It's Not Down in Any Map

Around midnight, while painting up some fresh art deco inspire designs, I had a sudden though about Supernatural, which happens on occasion (perhaps more occasions than I would be willing to admit in public).

Angels have the ability to possess people through hereditary lines (Michael can possess both John and Dean, Castiel can possess both Jimmy and his daughter). Now I know that this is going to be a shocker to everyone: Sam and Dean are full-blood brothers (they have the same biological sperm and egg donors that created them).

This means that both Sam and Dean have the same hereditary lines - logically, if angelic possession depends upon some sort of supernatural genetic factor, both Sam and Dean should have the ability to be possessed by Michael or Lucifer.

What if - with Dean's exhaustion, apathy, and general depression and Sam's fervor, anger, and need to explode things with his brain - Dean ends up as Lucifer's vessel and Sam as Michael? Logically speaking, if we take Michael's metaphor of the fallen brother vs the unfallen one, Dean is the one who went to Hell. Sam's made mistakes, but he's still alive and good Lord, Sam Winchester could make a career out of being sorry.